So this site is dedicated to the design of a ZX Spectrum Clone. In true research lab fashion this site will document the complete progress: the questions, the answers, the mistakes and the eureka moments.

The ZX Spectrum ULA: How to design a microcomputer is on sale NOW. 324 pages detailing the design and implementation of the ZX Spectrum ULA, and the techniques involved in the development of a home microcomputer.

The ZX Spectrum demonstrates a particular Z80 wait period. This must be faithfully reproduced if all games are to run successfully. The Spectrum ULA stops clocking the CPU with CLK held high whenever it needs access to the video memory at the same time as the CPU.

The ZX Spectrum keyboard consists of 40 keys arranged as 4 rows of 10. Internally these are treated as 8 half-rows of 5 keys. The keyboard is read by reading from port 0xFE - however the upper eight address lines play a role in determining which half row is to be read.

Jul 30, 2010 · The writing and production of The ZX Spectrum ULA: How to design a microcomputer has been completed and the book is with the printer. Once proof copies have been checked, distribution will begin! Read More

The ZX Spectrum ULA: How to design a microcomputer book gives a thorough discussion of Ferranti, their ULA and a detailed examination of every functional unit of the Sinclair design.

A vast amount of research has been carried out over the last six months into Ferranti, their ULA technology and fabrication, the Spectrum ULA design and the differences between the 5C and 6C ULA's. It has been a fascinating journey of discovery!

The writing and production of The ZX Spectrum ULA: How to design a microcomputer has been completed and the book is with the printer. Once proof copies have been checked, distribution will begin! Read More

The 48K ZX Spectrum handles all cassette IO through a single ULA pin, as well as the internal speaker. The significant bits of port 0xFE are (see interfaces for further information).

The ZX Spectrum ULA is an essential read for the electronics hobbyist, student or electronic engineer wishing to design their own retro-style microcomputer or anyone with an interest in historical micro-electronic and digital design.